Many applications in science and industry require an apparatus that creates a controlled amount of a fluid introduced into another fluid. For instance, some material corrosion testing applications require such an apparatus to determine the reaction of a material over time upon exposure to a controlled corrosive vapor-gas mixture. While various systems may be used to provide blends of two or more fluids, most such systems involve electrically-driven and/or electronically-monitored devices. A special circumstance occurs where it is necessary to provide a controlled amount of moisture in an environment that contains explosive gases. In this environment the use of electrically-driven and/or electronically-monitored devices would likely introduce a risk of explosion from an inadvertent electrical spark. Furthermore there are circumstances such as remote locations where a blend of fluids is needed and electricity is not available. What are needed therefore are methods and systems for providing a controlled blend of fluids without using electricity.